Radio frequency communication network having adaptive communication parameters

ABSTRACT

Improved apparatus for a radio communication network having a multiplicity of mobile transceiver units selectively in communication with a plurality of base transceiver units which communicate with one or two host computers for storage and manipulation of data collected by bar code scanners or other collection means associated with the mobile transceiver units. The radio network is adaptive in that in order to compensate for the wide range of operating conditions a set of variable network parameters are exchanged between transceivers in the network. These parameters define optimized communication on the network under current network conditions. Examples of such parameters include: the length and frequency of the spreading code in direct-sequence spread spectrum communications; the hop frame length, coding, and interleaving in frequency-hopping spread spectrum communications; the method of source encoding used; and the data packet size in a network using data segmentation. The invention is preferably to be applicable as an upgrade of an existing data capture system wherein a large number of hand-held transceiver units operate over an extensive area to gather data in various places, requiring the use of multiple base stations. In a variety of such installations such as warehouse facilities, distribution centers, and retail establishments, it may be advantageous to utilize not only multiple bases capable of communication with a single host, but with multiple hosts as well.

AUTHORIZATION PURSUANT TO 37 C.P.R. 1.71(d) AND (e)

[0001] A portion of the disclosure of this patent document containsmaterial which is subject to copyright protection. The copyright ownerhas no objection to the facsimile reproduction by anyone of the patentdocument or the patent disclosure, as it appears in the Patent andTrademark Office patent file or records, but otherwise reserve allcopyright rights whatsoever.

INCORPORATION BY REFERENCE

[0002] The following patent applications are incorporated in theirentirety by reference:

[0003] 1. abandoned application of Charles D. Gollnick, et al., U.S.Ser. No. 07/857,603 filed Mar. 30, 1992 (Attorney Docket Nos. DN37834XA;92 P 327);

[0004] 2. pending U.S. patent application of Meier, et al., Ser. No.______, filed Oct. 30, 1992 (Attorney Docket Nos. DN37882YA; 92 P 758);

[0005] 3. abandoned application of Ronald L. Mahany, U.S. Ser. No.07/485,313 filed Feb. 26, 1990 (Attorney Docket Nos. DN36500Y; 91P349);

[0006] 4. pending application of Steven E. Koenck, et al., U.S. Ser. No.07/305,302 filed Jan. 31, 1989 (Attorney Docket Nos. DN36649; 91 P 422);

[0007] 5. application of Ronald L. Mahany, et al., U.S. Ser. No.07/389,727 filed Aug. 4, 1989 (Attorney Docket Nos. DN36500X; 91P258),now issued as U.S. Pat. No. 5,070,536 on Dec. 3, 1991;

[0008] 6. application of Marvin L. Sojka, U.S. Ser. No. 07/292,810 filedJan. 3, 1989 (Attorney Docket Nos. DN36625X; 91P420), now issued as U.S.Pat. No. 4,924,462 on May 8, 1990; and

[0009] 7. European Published Patent Application EPO 353759 publishedFeb. 7, 1990.

BACKGROUND OF THE INVENTION

[0010] The present invention in a preferred implementation relates toimprovements in radio data communication networks wherein a number ofmobile transceiver units are to transmit data to a number of basestations under a wide range of operating conditions. To compensate forthe wide range of operating conditions, adaptability has been providedusing an exchange of parameters that define the nature of the networkcommunication. The invention is preferably to be applicable as anupgrade of an existing data capture system wherein a number of hand-heldtransceiver units of an earlier design are already in the fieldrepresenting a substantial economic investment in comparison to the costof base stations, accessories and components. In installations spreadover an extensive area, a large number of mobile portable transceiverunits may be employed to gather data in various places and multiple basestations may be required. In a variety of such installations such aswarehouse facilities, distribution centers, and retail establishments,it may be advantageous to utilize not only multiple bases capable ofcommunication with a single host, but with multiple hosts as well.

[0011] An early RF data collection system is shown in Marvin L. Sojka,U.S. Pat. No. 4,924,462 assigned to the assignee of the presentapplication. This patent illustrates (in the sixth figure) a NORAND®RC2250 Network Controller which supports one base transceiver forcommunication with multiple mobile portable transceivers. The exemplaryprior art device is capable of communicating with a host computerthrough an RS232C interface at up to 19,200 baud in asynchronous mode.In order for an optional RS422 interface to be substituted for an RS232Cinterface, the unit must be opened and substitute circuitry componentsinstalled within it.

SUMMARY OF THE INVENTION

[0012] The present invention provides an improved data communicationsystem which maintains RF communication links between one or more hostcomputers and one or more base transceiver units, each of which may becommunicative with many mobile portable transceiver units being movedabout a warehouse complex for the collection of data. Specifically, theinvention provides a data communication system for collecting andcommunicating data in the form of RF signals which has a plurality of RFtransceivers that store and modify at least one variable operatingparameter. From the stored parameter(s), each of transceivers controlthe operation of transmission and reception. The transceivers alsoevaluate the effect of the stored parameter based by analyzing eachtransmission received, and determine whether to make changes in thestored parameter. If changes are needed, the transceivers, modify andstore the modified operating parameter and begin operation basedthereon.

[0013] The operating parameters involve: 1) the size of data segments tobe transmitted; 2) the length or frequency of the spreading code usedfor direct-sequence spread spectrum communication; 3) the hopping rate,coding, and interleaving for frequency-hopping spread spectrumcommunication; and 4) the type of RF source encoding used.

[0014] In addition, the RF transceivers used in the data communicationnetwork of the present invention use system-default values to reset theoperating parameters if a series of failed communication exchangesoccurs, so that communication can be re-established.

[0015] It is therefore an object of the invention to provide an adaptiveradio communication system which permits the interconnection of one ortwo host computer devices to a multiplicity of base transceiver unitswhich may include both prior art existing installed units and newgeneration units capable of spread spectrum radio transmission.

[0016] It is a further object of the invention to provide an adaptive RFdata communication system which optimizes communication based on a setof operating parameters.

[0017] It is a further object of the invention to provide an adaptive RFdata communication system which maintains communication based on a setof operating parameters for optimizing communication, wherein theoperating parameters involve: 1) the size of data segments to betransmitted; 2) the length or frequency of the spreading code used fordirect-sequence spread spectrum communication; 3) the hopping rate,coding, and interleaving for frequency-hopping spread spectrumcommunication; and 4) the type of RF source encoding to be used.

[0018] It is a further object of the invention to provide a radiocommunication system network controller which via a communicationexchange optimizes a set of operating parameters, yet returns theparameters to their previous or system-default values upon failedcommunication.

[0019] These and other objects of the invention will be apparent fromexamination of the detailed description which follows.

DESCRIPTION OF THE DRAWING FIGURES

[0020]FIG. 1 is a block diagram of the prior art data communicationsystem.

[0021]FIG. 2 is a perspective view of the invention.

[0022]FIG. 3 is a schematic representation of an exemplary radiocommunication system utilizing the invention.

[0023]FIG. 4 is a diagrammatic illustration of the control circuitryelements of the invention.

[0024]FIG. 5 is a rear elevation view of the invention.

[0025]FIG. 6 is a diagrammatic illustration of the application specificintegrated circuit of the invention.

[0026]FIG. 7 is a block diagram showing an exemplary implementation ofintelligent network and router transceiver units such as the networktransceiver units of FIG. 3.

[0027]FIG. 8 is a diagram of an RF system utilizing a network controlleraccording to FIGS. 2-6, with one of its network ports configured forcommunication with a second host, and another of its ports coupled witha multiplicity of RF transceivers via an adapter unit.

[0028]FIG. 9 is a diagram illustrating the use of two networkcontrollers according to FIGS. 2-6, configured for dual host computerseach, and having their relatively high data rate extended distancenetwork ports coupled with a multiplicity of intelligent network androuter transceiver units implemented according to FIG. 7.

[0029]FIG. 10 is a diagram similar to FIG. 9 but showing the pari ofcoupled network controllers interfaced to a common relatively high datarate system having multiple hosts (e.g.) a local area network of theEthernet type or equivalent e.g. fiber optic type.

[0030]FIG. 11 is a diagram similar to FIG. 10 but indicating the networkcontrollers being coupled to respective different high data ratemultiple host systems (e.g., token ring type local area networks orother individual networks e.g., fiber optic loop networks of thecollision-sense multiple-access type).

[0031]FIG. 12 is a view similar to FIG. 9 but intended todiagrammatically indicate a distribution of network and routertransceivers and other elements of an on-line RF data collection systemover an extensive area of a facility e.g. of one of the types previouslymentioned.

[0032]FIG. 13 shows an intelligent controller and radio base unit whichunifies controller and radio components such as shown in FIG. 7 into asingle housing of the size represented in FIGS. 2 and 5.

[0033]FIG. 14 shows a diagrammatic illustration of the signal processingfor two of four paiis of communication ports of the multiple baseadapter of the RF data collection system illustrated in FIG. 8.

[0034]FIG. 15 is a diagram of parts of an RF data collection systemutilizing a network controller according to FIGS. 2-6 and a multiplebase adapter according to FIG. 14, with eight base transceiver unitscoupled to the multiple base adapter.

DETAILED DESCRIPTION OF THE INVENTION

[0035]FIG. 1 shows an existing radio frequency data transmission system10 wherein a base station transceiver means 11 has a number of mobiletransceiver units such as 12A, 12B, . . . , 12N in radio communicationtherewith.

[0036] By way of example, the base station may be comprised of a radiobase unit 14 such as the model RB3021 of Norand Corporation, CedarRapids, Iowa, which forms part of a product family known as the RT3210system. In this case, the radio base 14 may receive data from therespective mobile RF terminals, e.g. of type RT3210, and transmit thereceived data via a network controller and a communications link 16(e.g. utilizing an RS-232 format) to a host computer 17.

[0037] The data capture terminals 12A, 12B, . . . , 12N may each beprovided with a keyboard such as 18, a display as at 19, and a bar codescanning capability, e.g., via an instant bar code reader such as shownin U.S. Pat. No. 4,766,300 issued Aug. 23, 1988, and known commerciallyas the 20/20 High Performance Bar Code Reader of Norand Corporation.

[0038]FIG. 2 provides a perspective view of the invention 40 in thepreferred embodiment case 20. Front panel 22 is provided with display 24and select key 26, up key 28 and down key 30. Power indicator 32comprises a low power green light emitting diode which is energized whenpower is supplied to the invention 10. Error condition indicator 34 is ayellow LED which is software controlled to be energized if the invention10 is in error condition.

[0039]FIG. 3 discloses a diagrammatic illustration of a radiocommunication system in accordance with the present invention. Inventionnetwork controller 40 is coupled to host computer 42 such that data maybe interchanged between the devices over host communications link 44,which may be either in an RS232C format or selectively in an RS422format. The host communication link 44 couples to controller 40 at hostport 46.

[0040] First communication port 48 of controller 40 provides means forcoupling of network 50 to controller 40. Network 50 comprises a numberof base RF transceiver units 52A, 52B and 53B, each of which may beselectively employed in the radio frequency communication of data frommobile transceiver units. It is to be understood that base transceiverunits 52 are designed and equipped to be operable in the exchange ofdata with network controller 40 over network link 56 such that each basetransceiver unit 52A, 52B, or 53C may independently exchange data withnetwork controller 40 through first communication port 48. When firstcommunication port 48 is intended for operation with a network such asnetwork 50 of base transceiver units 52A, 52B and 53C, for example,network controller 40 is selectively operated to provide an RS485interface at first communication port 48. First communication port 48may be alternately selected to operate as an RS232C interface, as anRS422 interface, as a proprietary NORAND® Radio One Node Networkinterface or as a high speed V.35 interface. The selection of interfaceto be provided at first communication port 48 is front panel controlled,that is, the user may operate front panel keys 28, 30 and 26 (See FIG.2) to direct the proper interface to be provided at first communicationport 48.

[0041] Base transceiver units 52A, 52B, and 52C are coupled to networklink 56 by serial means, rather than parallel means, and each may becaused to transmit or to receive independently from the others whileadditionally being communicative with network controller 40 in arandomly chosen fashion.

[0042] It is further to be understood that interface translation isprovided within controller 40 such that data communicated at firstcommunication port 48 may be directed to host 42 at port 46 via properlychosen interface means as is required by the host 42 with whichcommunication is intended.

[0043] Like first communication port 48, second communication port 57may be internally switched among interface choices of these types:RS232C, RS422, V.35, RS485 and proprietary NORAND® Radio One NodeNetwork interface. In the illustrated arrangement of FIG. 3, forexample, second communication port 57 is coupled over third link 53 topreviously installed base transceiver 54, which heretofore had been usedin a prior art system as is illustrated in FIG. 1. Because oflimitations of base transceiver 54, it must communicate via RS232Cinterface format and therefore, second communication port 57 must beselected to operate in RS232C interface mode. However, when secondcommunication port 57 is desired to communicate with a network via RS485interface, front panel keys 26, 28 and 30 may be manipulated by the userto provide the RS485 interface availability at second communication port57. Likewise, second communication port 57 may be selected to operate asan RS422 interface, as a V.25 interface, or as the proprietary NORAND®Radio One Node Network interface.

[0044] Diagnostic port 55 provides a fourth communication pathway fornetwork controller 40, providing an asynchronous port operable at 300 to19,200 baud as an RS232C interface. When desirable, diagnostic port 55may be coupled by diagnostic link 58 to diagnostic device 60 forpurposes of error diagnosis of controller 40 by diagnostic device 60, orfor reprogramming of memory devices within controller 40 when desired.It is contemplated that diagnostic device 60 comprises a 16 or 32 bitmicroprocessor commonly known as a personal computer or “PC”. The modeof coupling between diagnostic device 60 and network controller 40 maybe direct or through remote means by use of a modem.

[0045] Referring now to FIG. 4, a central processing unit 70 is providedwith at least four data communication ports, illustrated at numerals 71,72, 73, and 74. First data communication port 71 may be selectivelycoupled to RS232 interface member 76 or V.35 interface member 78. Thechoice of whether RS232 interface member 76 or V.35 interface member 78is chosen is dependent upon the operating characteristics presented bythe host computer, such as host computer 42 of FIG. 3, with whichnetwork controller 40 will communicate. The choice of whether firstcommunication port 71 is coupled to interface member 76 or to interfacemember 78 depends on the front panel selection made by the user by keys26, 28, and 30 shown in FIG. 2.

[0046] Second communication port 72 may be selectively coupled to RS232member 80 or to RS485 interface member 82 or to RS422 interface member84 or to NORAND® Radio One Node Network proprietary interface member 86.By use of front panel keys 26, 28, and 30 of FIG. 2, the user may selectsecond communication port 72 to be coupled to any one of interfacemembers 80, 82, 84, and 86.

[0047] Third communication port 73 is identical to second communicationport 72 in functionality, being selectively couplable to RS232 interfacemember 88, to RS485 interface member 90, to RS422 interface member 92 orto NORAND® Radio One Node Network proprietary interface member 94.

[0048] In the preferred embodiment of the invention 40, centralprocessing unit 70 of FIG. 4 comprises a Motorola™ 68302 integrated chipcooperative with an application specific integrated circuit. Centralprocessing unit 70 employs novel features allowing the bidirectional useof a data communicative line of the Motorola™ 68302 chip and a singleclock signal line to eliminate the need for coder-decoder members to beassociated with the Motorola™ 68302 chip while allowing the use of onlyone pair of signal wires to be coupled to the RS485 interfaces 82 and 90of FIG. 4.

[0049] Fourth communication port 74 of central processing unit iscoupled to asynchronous RS232 interface member 97 to be available forinterconnection of a diagnostic device therewith.

[0050] Also coupled to central processing unit 70 are display member 24and keyboard member 31 with which keys 26, 28, and 30 of front panel 22(FIG. 2) are interactive.

[0051] Memory elements including EPROM element 96, DRAM unit 98, FLASHmemory unit 100 and EEPROM element 102 are intercoupled with each otherand with central processing unit 70.

[0052] Power supply member 104 is selectively attachable to inventionnetwork controller 40. In order to avoid the necessity of differentmodels of network controller 40 depending on the local electrical powerutility's operating characteristics, power supply 104 is provided inoptional models depending on the country in which it is to be used,power supply 104 being capable of providing satisfactory output power tonetwork controller 40 regardless of the voltage or frequency of theinput source provided to power supply 104.

[0053] The application specific integrated circuit (ASIC) used in theinvention network controller 40 is disclosed in FIG. 6 and is identifiedby the numeral 120. ASIC 120 comprises a central processor unitinterface 122 member which is coupled to the central processor unit busby CPU bus link 124 which extends from ASIC 120. Also coupled to the CPUbus link 124 is dynamic random access memory (DRAM) timing element 126,which provides network controller 40 with timing signals for the DRAMmember 98 illustrated in FIG. 4 when memory refresh of the DRAM 98 isindicated. DRAM timing element 126 is also coupled exteriorly to theASIC 120 to DRAM member 98 by DRAM link 127.

[0054] Central processing unit interface 122 is coupled to asynchronoussignal processing element 128 by signal path 130. Asynchronous signalprocessing element 128 comprises a baud rate generator cooperative witha universal asynchronous receiver-transmitter.

[0055] Also coupled to central processing unit interface 122 is networkclock and control member 132 which comprises a programmable networkclock generator which can be selectively programmed to generate anoptional clock speed for a network to be coupled through RS485interfaces 82 and 90 seen in FIG. 4. Network clock and control member132 also provides detection means for detections of failure conditionson a linked network and provides control signals to system components inresponse thereto, including interrupt signals to programmable interruptcoordinator circuitry included in central processing interface 122.Network clock and controller member 132 provides data encoding by theFMO standard, then the encoded data may be operated upon by RS485interfaces 82 and 84 and transmitted and received by single twisted pairmeans to multiple serially networked base transceiver units exemplifiedby base transceiver unit 52A, 52B, and 52C illustrated in FIG. 3.

[0056] Keyboard controller element 134 is coupled to central processingunit interface and provides a link exterior to ASIC 120 to keyboard 31(See FIG. 3).

[0057] FLASH memory/EEPROM logic control member 136 is coupled tocentral processing unit interface 122 and comprises control functionsfor FLASH memory element 100 and EEPROM memory element 102 of FIG. 3.

[0058] Central processing unit interface 122 is also coupled by line 138to latches exterior to ASIC 120.

[0059] It is to be understood that the base transceiver units 52A, 52B,and 52C illustrated in FIG. 3 are communicative with mobile transceiverunits by electromagnetic radio means. The mobile transceiver units maybe associated with bar code scanning devices such as the NORAND® 20/20High Performance Bar Code Reader whereby the scanning devices scan anobject having a bar code associated therewith and collect informationstored in the bar code, which information is then transmitted throughthe mobile transceiver units to base transceiver units such as basetransceiver units 52A, 52B, and 52C or base transceiver unit 54 of FIG.3. The bar code data received by said base transceiver units is thentransmitted in the example of FIG. 3, over network 50 by basetransceiver units 52A, 52B, or 52C, or over link 53 by base transceiverunit 54, to network controller 40 which performs the routing anddelivery of the data to the stationary data processor, or processors,such as shown for example, by host 42 of FIG. 3.

[0060] Description of FIGS. 7 through 11

[0061]FIG. 7 shows a block diagram of a particularly preferredintelligent base transceiver unit known as the RB4000. It will beobserved that the components correspond with components of the networkcontroller of FIG. 4, and similar reference numerals (preceded by 7-)have been applied in FIG. 7. Thus, the significance of components 7-70through 7-73, 7-76, 7-82, 7-96, 7-98, 7-100 and 7-104 will be apparentfrom the preceding description with respect to FIG. 4 and 6, forexample. I/O bus 700 may be coupled with a spread spectrum transmission(SST) or ultra high frequency (UHF) transceiver 701 which may correspondwith any of the transceivers of units 52A, 52B, 52C or 54 previouslyreferred to. The network controller 70 could have a similar RFtransceiver coupled with its data port 72 or 73 and controlled viainput/output bus 400, e.g. for direct RF coupling with routertransceivers such as 901, 901, FIG. 9.

[0062] Referring to FIG. 8, a network controller 40 is shown with port71 configured for interface with a host port type SNA V. 35 56K/64K bitsper second. Port 72 is shown as configured for communication with apersonal computer of the PS/2 type operating asynchronously at 38.4Kbits per second. Port 74 is coupled with a modem 8-60 providing forremote diagnostics and reprogramming of the network controller 40.

[0063] Port 73 of network controller 40 is shown as being connected withan adapter component 801 known as the MBA3000. A specification for theMBA3000 if found in Appendix A following this detailed description. Inthe operating mode indicated in FIG. 8, the adapter 801 serves to couplecontroller 40 sequentially with four radio base transceiver units suchas indicated at 811 through 814. Component 811 is a commerciallyavailable radio base known as the RB3021 which utilizes features ofSojka U.S. Pat. No. 4,924,462 and of Mahany U.S. Pat. No. 4,910,794 bothassigned to the present assignee, and the disclosures of which arehereby incorporated herein by reference in their entirety. Base station811 may communicate with a multiplicity of hand-held RF data terminalssuch as indicated at 821. Details concerning base transceiver units 812and 813, 814 are found in the attached Appendices B and C, respectively.Base 814 is indicated as being coupled with the adaptor 801 via RFbroadband modems 831 and 832. Base units 813 and 814 may communicatewith a variety of mobile transceiver units such as those indicated at833 and 834 which are particularly described in Appendices D and E.

[0064]FIG. 9 shows two network controllers 40A and 40B each with itshost ports configured as with the controller 40 of FIG. 8. In thisexample, the second ports 72 of the controllers 40A and 40B areconfigured for communication a relatively high data rate relativelyalong a distance network channel 56 which may have the characteristicsof the serial channel 56 of FIG. 3, for example, an RS485 channeloperating at 384 kilobits per second (384K bps). Network basetransceivers 52A, 52B and 52C may correspond with the correspondinglynumbered transceiver units of FIG. 3, for example, and the network mayhave additional network transceivers such as 52D. Furthermore, thenetwork transceivers may have RF coupling with router transceiver unitssuch as indicated at 901, 902 and 903. Router transceiver unit 902 isillustrated as a RB4000 intelligent transceiver such as represented inFIG. 7 and having its input/output bus 700 coupled with a peripheral.

[0065]FIG. 10 is entirely similar to FIG. 9, for example, except thatports 72 of the controllers 40A and 40B are coupled with separate serialtype high data rate network channels, and ports 73 of the respectivenetwork controllers are coupled to a very high speed network e.g. in theseveral megabits per second range such as an Ethernet local area network1000. Suitable interfaces are indicated at 1001 and 1002.

[0066]FIG. 11 is entirely similar to FIG. 9 except that the ports 73 ofthe network controllers 40A and 40B are coupled with respective localarea ring type networks which may be separate from each other and eachhave two or more hosts such as represented in FIG. 9 associated with therespective ring networks such as token rings 1100A and 1100B. Suitableinterface means are indicated at 1101 and 1102.

[0067] Description of FIG. 12

[0068]FIG. 12 shows, for example, two network controllers 40A and 40B,each with two host computer units such as 42-1A. Host 42-2A is shownwith a printer or other peripheral P1 which may generate bar codes, forexample, for replacement of damaged bar codes or the like. Anotherprinter P2 is shown associated with base 52C, again for example, forproducing bar code labels where those are needed in the vicinity of abase station. In a large warehouse, relatively large distances may beinvolved for a worker to return to a printer such as P1 to obtain a newbar code label. Thus, it may be very advantageous to provide a printerP2 at the base station 52C which may be relatively close to a processinglocation which requires printed labels, e.g. a processing location inthe vicinity of hand-held terminal 12-2 in FIG. 12. A base 52F may havea peripheral P3 associated therewith such as a large screen display, aprinter or the like which may supplement the capabilities of a hand-heldterminal, for example printing out new bar code labels at a convenientlocation, or providing a full screen display, rather than the morelimited screen display area of the hand-held terminal 12-2.

[0069] If, for example, a base radio 52D which might be located at theceiling level of a warehouse became inoperative at a time when qualifiedrepair personnel were not immediately available, with the present systemit would be feasible to provide a substitute base radio or base radios,for example, as indicated at 52D1 located at table level or the like.

[0070] With the present system, the base radio stations do notnecessarily forward data communications received from a given terminalto a particular host. For example, hand-held terminal 12-2 may request apath to printer P2, and such a path may be created via base stations52D1 and 52C. Station 52C upon receipt of the message form terminal 12-2would not transmit the message to a host but would, for example, producethe desired bar code label by means of printer P2. Further, terminal12-2 may have provision for digitizing a voice message which might, forexample, be addressed to terminal 12-1. The system as illustrated wouldbe operable to automatically establish a suitable path for example, viastations 52D1, 52C, 52B, 52E and 12-1 for the transmission of this voicemessage in digital form. Successive segments of such a voice messagewould be stored, for example, by the terminal 12-1, and when thecomplete message was assembled, the segments would be synthesized into acontinuous voice message for the user of terminal 12-1 e.g. by means ofa speaker 1201 also useful for sending tone signals indicating valid barcode read, etc.

[0071] In accordance with the present invention, a hardware system suchas illustrated in FIG. 12 may be physically laid out and then uponsuitable command to one of the network controllers such as 42-2B, theentire system would be progressively automatically self-configured forefficient operation. For example, controller 40B could successively tryits communications options with its output ports such as 71-73,determining for example, that host processors were coupled with ports 71and 72, one operating on a 38.4 kilobit per second asynchronous basisand the other presenting a SNA port for the V.35 protocol at 64 kilobitsper second. For example, on host, 42-1B might be a main frame computer,while the other host 42-2B might be a PS/2 type computer system. Thecontroller 40B having thus automatically configured itself so as to becompatible with the devices connected to ports 71 and 72, could proceedto transmit via port 73 a suitable inquiry message to the networkchannel 56. Although a polling protocol is preferred, each of the basestations could operate, for example, on a carrier-sense multiple-access(CSMA) basis or using a busy tone protocol to respond to the inquirymessage from the controller 40B, until each of the successive bases onthe network had responded and identified itself. Each base, for example,would have a respective unique address identification which it couldtransmit in response to the inquiry message so as to establish itspresence on the network.

[0072] The controller 40B could then transmit auto configure commands tothe successive bases in turn, instructing the bases to determine whatperipherals and router bases such as 52D1, 52E and 52F were within therange of such base, and to report back to the controller. For example,bases such as 52C and 52F could determine the nature of peripherals P2and P3 associated therewith so as to be able to respond to an inquiryform a terminal such as 12-2 to advise the terminal that a bar codeprinter, for example, was within direct RF range.

[0073] In the case of a breakdown of a component of the system such as52D, it would merely be necessary to place a router device such as 52D1at a convenient location and activate the unit, whereupon the unit couldsend out its own broadcast inquiry which, for example, could be answeredby the base stations 52C and 52F, station 52C in turn, advising arelevant host or hosts of the activation of a substitute router station.Thus, the system is conveniently re-self-configured without thenecessity for a technician familiar with the particular configurationprocedure. As another example, where the base stations are operatingutilizing spread spectrum transmission, the introduction of barriers(such as a new stack of inventory goods) to such transmission between agiven base such as 52A and various terminals, could result in the base52A contacting router 52E, for example, with a request to become activewith respect to the blocked terminals.

[0074] A more detailed example of auto-configuration of the network canbe found in pending U.S. patent application of Meier, et al., Ser. No.______ (Attorney Docket Nos. DN37882YA; 92 P 758) filed Oct. 30, 1992,which is incorporated herein by reference.

[0075] Description of FIG. 13

[0076]FIG. 13 shows an intelligent integrated controller and radio baseunit 1300 which is integrated into a single housing or case 1301corresponding to the case or housing 20 of FIG. 2. the housing 1301 maybe provided with an external antenna as diagrammatically indicated at1302 with suitable RF coupling to the radio circuitry indicated at 1303.Components 13-70 through 13-74, 13-76, 13-78, 13-96, 13-97, 13-98,13-100, and 13102 may correspond with the correspondingly numberedcomponents described with reference to FIG. 4.

[0077] Supplementary Discussion

[0078] In accordance with the present disclosure, a network controller,or integrated network controller and radio unit is coupled to one ormore host computers via a standard interface such as commonlyencountered in practice (e.g. RS232, V. 35, Ethernet, token ring, FDDI,and so on). In this way, no specialized interface or adapter is requiredfor the host.

[0079] Since the preferred network controller can connect to two hosts,if one host is detected to have failed, or in the event of a systemcrash, loss of communication link, or the like, the network controllercan automatically switch to the second host. The second host may be atruly redundant system, or may be a simpler computer of the PC type (aso-called personal computer) that can simply store transactions untilthe main host is restored. As another example, a single host may have asecond port coupled to a second port of the controller especially if acommunication link failure may be a problem. For example, two ports ofthe network controller may be coupled by separate modems with separatephone lines, leading to separate ports of a single mainframe computer,for example an IBM3090. In a fully redundant system, two ports of anetwork controller may be connected respectively to two mainframecomputers such as the IBM3090.

[0080] The disclosed network controller can also connect one radionetwork to two hosts using RS232or V.35 ports or to many hosts using alocal area network such as Ethernet, token ring, or FDDI. A number ofthe disclosed network controllers (for example, up to thirty-two) can beconnected together to interface many hosts to a single radio network.The hand-held portable terminals in such a network can then talk to anyof the hosts they choose.

[0081] For example where one port of the disclosed network controller iscoupled via its RS232 interface to a mainframe computer such as theIBM3090, another of its ports may be coupled via an FDDI network with asuper computer e.g. the Cray X-MP. Then mobile and/or portable terminalscan access either the main frame or the super computer, or in general,any of the hosts that are connected to the network controller.

[0082] As indicated in FIG. 9, four hosts can be on one network.Referring to FIGS. 10 and 11, a multiplicity of hosts may be coupledwith each local area network so as to be in communication with one ormore of the disclosed network controllers. Furthermore, a singledisclosed network controller can control two radio networks such as theone indicated at 50 in FIG. 3. Where each network such as 50 is limitedto thirty-two devices, the number of devices is doubled with the use oftwo radio networks. Two such radio networks may also be utilized for thesake of redundancy, with a provision for automatic switch-over from oneradio network to the second if a problem develops on the first. Tworadio networks may also facilitate the use of different radiotechnologies in one installation.

[0083] The various multi-drop local area networks referred to herein,for example at 7-82 in FIG. 7 and as represented at 56, 56A, 56B, FIGS.9 through 12, and at 13-82 in FIG. 13 may comprise HDLC based local areanetworks operating at up to 2.5 megabits per second and using biphasespace encoding (FMO) for clock recovery from data.

[0084] The components 86 and 94, FIG. 4, and component 13-11, FIG. 13,provides a low-cost base radio interface using three pairs of twistedconductors. One pair provides a bidirectional RS485 data line. Anotherpair is used for the clock and has an RS422 electrical configuration,and is one directional from the radio to the controller. The thirdtwisted pair is also RS422 and is used to communicate from thecontroller to the radio transceiver to effect mode selection.

[0085] Since it is advantageous to operate the network and router RFtransceiver units so as to be compatible with existing mobile datacollection terminals such as shown in Appendix D1 et seq., a preferredmode of operation is based on the RTC protocol as disclosed in theaforementioned incorporated Mahany and Sojka patents and the followingapplications:

[0086] (1) U.S. Ser. No. 07/389,727 filed Aug. 4, 1989 (Attorney DocketNos. 36500X; 91 P 258), now issued as U.S. Pat. No. 5,070,536 on Dec. 3,1991.

[0087] (2) European Published Patent Application EPO 353759 publishedFeb. 7, 1990.

[0088] (3) U.S. Ser. No. 07/485,313 filed Feb. 26, 1990 (Attorney DocketNos. 36500Y; 91 P 349).

[0089] The disclosures of applications (1), (2) and (3) are herebyincorporated herein by reference in their entirety.

[0090] An aspect of the invention resides in the provision of a networkcontroller having port means selectively configurable for coupling infirst mode with network RF transceiver units at a relatively high datarate such as 100 kilobits per second or higher, and for coupling in asecond mode with network transceiver units at a relatively low data ratesuch as about twenty kilobits per second. Preferably a single port meanssuch as 2, 3, or 5, 6, FIG. 5, can be software configured to interfaceselectively in the first mode or in the second mode. It is presentlyless expensive to use multiple connectors per port rather than a single37-pin connector for example.

[0091] Where a network controller such as 40 operates two high data ratenetworks, for example, one network of RF base transceivers could operatewith the RTC protocol, and the second network could operate according toa different protocol such as that disclosed in pending application Ser.No. 07/660,618 filed on or about Feb. 25, 1991 (Attorney Docket No.37734), in its entirety. It will be apparent that many modifications andvariations may be effected without departing from the scope of theteachings and concept of the present disclosure.

[0092] Description of FIGS. 14 and 15

[0093]FIG. 14 is a block diagram of the circuitry for one pair ofcommunication ports 1401 and 1403 of adapter 801 (FIG. 8) for use incoupling to base transceiver units. Three additional pairs ofcommunication parts for coupling to six additional base transceiverunits are provided in the preferred embodiment of adapter 801 asexemplified by the MBA3000 Multiple Base Adapter further described inAppendix A. It is to be understood that the circuit components coupledto each additional pair of communication ports of adapter 801 isidentical to that shown for first port pair 1A/1A, that is ports 1401and 1403 of FIG. 14. The adapter 801 provides means for connecting thecontroller 40 (FIG. 8) at its port 73 to a multiplicity of radio baseunits illustrated in FIG. 8 as, for example, 811, 812, 813, 814,including in selected pairs. In the preferred embodiment of adapter 801,up to eight radio base units may be coupled through use of adapter 801to a network controller 40, to be controlled by controller 40 inselected pairs thereof. The controller 40 may control the radio baseunits such as 811, 812, 813, 814, (FIG. 8) in simulcast mode, that is,with all base radios interrogating mobile transceiver units such as 821,833, and 834 of FIG. 8 simultaneously, or with the base units beingemployed in pairs to interrogate the mobile transceiver units.

[0094] Referring again to FIG. 14, the network controller 40 providestransmit data and baud rate select signals to adapter 801. Withinadapter 801, the controller outputs are converted to TTL levels by TTLconverter 1402 and they are then provided to buffer 1404 which providesthe signals to paired RS232 transceivers 1406 and 1408, and to pairedRS422 transceivers 1410 and 1412 which deliver the converted signals toports 1401 and 1403 respectively. By this means, the controller's outputsignals are provided to a pair of output ports 1401 and 1403 in bothRS232 and RS422 interface at the same time. An additional threeoutput-port-pairs are provided which may be denominated 2A/2B, 3A/3B and4A/4B, which ports are controlled and operated identically to ports1A/1B identified in FIG. 14 as ports 1401 and 1402. The RS232transceivers 1406 and 1408 and RS422 transceivers 1410 and 1412 andports 1401 and 1403 are illustrative of all circuitry coupled to portpairs of adapter 801.

[0095] Similarly, signals provided to adapter 801 by base radios coupledto the output port pairs, e.g. ports 1401 and 1403 of FIG. 14, are firstconverted to TTL levels by the RS232 transceivers 1406 and 1408 or bythe RS422 transceivers 1410 and 1412, depending upon which interface ispresented by a pair of base radios at port 1401 and 1403. The signalsprovided to adapter 801 are then forwarded by the transceivers 1406 and1408 or 1410 and 1412 at TTL levels to controller 40. A selection unit1414 provides a push-to-talk selection signal to the RS232 transceivers1406 and 1408 and to the RS422 transceivers 1410 and 1412 to provide PTTselection signals at ports 1401 and 1403 in both RS232 and RS422 format.It is to be understood that similar selection units are associated withremaining port pairs 2A/2B, 3A/3B. 4A/4B so that the ports may beindependently operated.

[0096] The adapter 801 of FIG. 8 is exemplified by the MBA3000 multiplebase adapter unit manufactured by the NORAND Corporation of CedarRapids, Iowa as shown in Appendix A. Because of the operation of theMBA3000 multiple base adapter by dual methods in either RS232 or RS422signal environments, the MBA3000 may be incorporated into systems havingexisting installed base radios which present only an RS232 interface orit may be incorporated into systems having base radios some of whichoperate at RS422 and some at RS232.

[0097]FIG. 15 illustrates a preferred arrangement of controller 40 andadapter 801 when used in an environment with multiple base radios inmultiple warehouse environments. Controller 40 is coupled to adapter 801which is coupled to paired bases 1511, 1512; 1513, 1514; 1515, 1516; and1517, 1518; which are located in warehouses 1501, 1502, 1503 and 1504.By geographical separation in warehouse 1501, for example, base radios1511 and 1513 provide substantial coverage of warehouse 1501 such that amobile transceiver being used within warehouse 1501 would becommunicated with by either base radio 1511 or 1513. By the use ofadapter 801, controller 40 may cause interrogation simultaneously bybase radios 1511, 1512, 1513, 1514, 1515, 1516, 1517, 1718, or it maycause sequential interrogation by radio pairs 1511/1512, 1513/1514,1515/1516, or 1517/1518 in succession. When a mobile transceiverresponds by RF communication means with a base radio, e.g. base radio1511, the response is transmitted by base radio 1511 through coupling1521 to adapter 801 which automatically converts the incoming responseto RS232 interface as necessary, to make it suitable for reception bycontroller 40.

[0098] Through a system as exemplified in FIG. 15, data collection froma number of roving mobile transceivers may be initiated by a networkcontroller 40 through a four-warehouse environment. When basetransceiver units 1511 and 1512 have been unsuccessful in establishingcommunication with the desired mobile transceiver unit, controller 40will then cause bases 1513 and 1514 to attempt communication and ifbases 1513 and 1514 are unsuccessful, controller 40 will proceed throughthe other base radio pairs, namely 1515/1516 and 1517/1518, as needed,to establish communication with the desired mobile transceiver unit.Details regarding base transceiver units 1511, 1512, 1513, and 1514 arefound in Appendix B. Details regarding base transceiver units 1515,1516, 1517, and 1518 are found in Appendix D.

[0099] The adapter 801 is provided to operate in either simulcast orsequential mode. In the normal or simulcast mode, adapter 801 allows theuse of one to eight bases, where the bases are configured as four pairsof two bases. In this mode the adapter 801 simulcasts to a single basepair at a time and the four sets of base pairs are selected using adynamic time-division multiplexing method. The user can configure theadapter 801 to use any of the eight base ports, using simulcasting ortime-division multiplexing to best advantage.

[0100] There are two sets of base transceiver units, referred to as setA (identified as 1A, 2A, 3A, and 4A) and set B (identified as 1B, 2B,3B, and 4B). Within a set, the base transceiver units are selected bytime-division multiplexing.

[0101] It can be seen in FIG. 15, that there are four pairs of basetransceiver units defined as pairs 1A/1B, 2A/2B, 3A/3B, 4A/4B. Each basetransceiver unit of a base pair is simulcasted to at the same time.

[0102] The hardware of the adapter 801 allows the selection of the basepairs (pair 1A/1B through 4A/4B) using control lines from the controller40. Adapter 801 transmits to both base transceiver units of a base pairat the same time and receives independently from each basesimultaneously.

[0103] The use of adapter 801 allows an extension of the number of basetransceiver units that can be used in a facility to allow for adequatecoverage, it is important to understand how the base transceiver unitsoperate when simulcasting is used, and when time-division multiplexingis used.

[0104] The adapter 801 distributes signals transmitted by controller 40to base transceiver pairs at the same time, so if there is an overlap inthe coverage for the two base transceiver units, there may be someinterference. The amount of interference depends on the relative signalstrengths; if the strength is similar in one spot the chance ofinterference is larger that if the signal strengths are different. Thistype of interference could be avoided in some configurations bysplitting coverage areas of pairs of base transceiver units. Anothermethod of covering the overlap area is to place another base (not one ofthe base pairs) to cover the overlap area. The radio signals from themobile transceiver unit may be picked up fully or partially by either orboth base transceiver units of a given pair. However the adapter 801first tries to receive from one base transceiver unit, for example base1511, and if unsuccessful, it then switches to try to receive from asecond base transceiver unit, for example base transceiver unit 1513. Ifthe information is successfully received from the first base transceiverunit, the information from the second base transceiver unit is ignored.Thus the controller assures data does not get sent to the host dataprocessor in duplicate.

[0105] The user may couple from one to eight base transceiver units tothe adapter 801 and can then configure those base transceiver units asrequired to meet the installation's needs. Any combination of ports ofthe adapter 801 can be used. Thus the user can take advantage of theability to simulcast or sequentially (via time-division multiplexing)access the base transceiver units 1511, 1512, 1513, 1514, 1515, 1516,1517, and 1518.

[0106] The following Appendix E provides an exemplary computer programlisting for preferred control instruction for the system disclosedherein.

[0107] Multipath Fading and Data Packet Size Parameters.

[0108] In a preferred embodiment, the data (or messages) to be sentthrough the RF communication link is segmented into a plurality of DATApackets and is then transmitted. Upon receipt, the DATA packets arereassembled for use or storage. Data segmentation on the RF linkprovides better communication channel efficiency by reducing the amountof data loss in the network. For example, because collisions betweentransmissions on an RF link cannot be completely avoided, sending thedata in small segments results in an overall decrease in data loss inthe network, i.e., only the small segments which collide have to bere-sent.

[0109] Similarly, choosing smaller data packets for transmission alsoreduces the amount of data loss by reducing the inherent effects ofperturbations and fluctuations found in RF communication links. Inparticular, RF signals are inherently subject to what is termed“multi-path fading”. A signal received by a receiver is a composite ofall signals that have reached that receiver by taking all availablepaths from the transmitter. The received signal is therefore oftenreferred to as a “composite signal” which has a power envelope equal tothe vector sum of the individual components of the multi-path signalsreceived. If the signals making up the composite signal are ofamplitudes that add “out of phase”, the desired data signal decreases inamplitude. If the signal amplitudes are approximately equal, aneffective null (no detectable signal at the receiver) results. Thiscondition is termed “fading”.

[0110] An data communication system using segmentation can be found in apending application of Steven E. Koenck, et al., U.S. Ser. No.07/305,302 filed Jan. 31, 1989 (Attorney Docket Nos. DN36649; 91 P 422),which is incorporated herein by reference in its entirety. Specificreference is made to Appendix A thereof.

[0111] Normally changes in the propagation environment occur relativelyslowly, i.e., over periods of time ranging from several tenths (1/10's)of seconds to several seconds. However, in a mobile RF environment,receivers (or the corresponding transmitters) often travel over somedistance in the course of receiving a message. Because the signal energyat each receiver is determined by the paths that the signal componentstake to reach that receiver, the relative motion between the receiverand the transmitter causes the receiver to experience rapid fluctuationsin signal energy. Such rapid fluctuations can result in the loss of dataif the amplitude of the received signal falls below the sensitivity ofthe receiver.

[0112] Over small distances, the signal components that determine thecomposite signal are well correlated, i.e., there is a small probabilitythat a significant change in the signal power envelope will occur overthe distance. If a transmission of a data packet can be initiated andcompleted before the relative movement between the receiver andtransmitter exceeds the “small distance”, data loss to fading isunlikely to occur. The maximum “small distance” wherein a high degree ofcorrelation exists is referred to hereafter as the “correlationdistance”.

[0113] As expressed in wavelengths of the carrier frequency, thecorrelation distance is one half ({fraction (1/2)}) of the wavelength,while a more conservative value is one quarter ({fraction (1/4)}) of thewavelength. Taking this correlation distance into consideration, thesize of the data packet for segmentation purposes can be calculated. Forexample, at 915 MHz (a preferred RF transmission frequency), a quarterwavelength is about 8.2 centimeters. A mobile radio moving at ten (10)miles per hour, or 447 centimeters per second, travels the quarterwavelength in about 18.3 milliseconds. In such an environment, as longas the segment packet size remains well under 18.3 milliseconds,significant signal fluctuations during the duration of a packettransmission is unlikely. In such an preferred embodiment, five (5)millisecond data packet segments are chosen which provides aquasi-static multipath communication environment.

[0114] The faster the relative movement between a transmitter and areceiver the greater the effect of fading, and, therefore, the smallerthe data segment should be. Similarly, if the relative movement isslower, the data segment can be larger.

[0115] Slower fading effects which might be experienced betweenstationary transceivers in an office building due to the movement ofpeople, mail carts, and the like. In a typical application of thepresent invention, the RF transceiver of a mobile unit may be securedwith a bar-code scanner such as a deflected laser beam bar-code scanneror an instant CCD bar-code scanner. In such an example, the bar codedata could be transmitted to the base station as the RF transceiver anda scanner device were being jointly transported by a vehicle (e.g. aforklift truck) to another site, or the RF transceiver and a scanner,e.g. as a unitary hand-held device, could be carried by the operator toanother site as the bar code data was being transmitted to the basestation. In such situations, fading is more pronounced.

[0116] If fading does not pose a problem on a given network, theoverhead associated with segmentation, hand-shaking and reconstructionmay not be justifiable. However, where fading exists, such overhead maybe required.

[0117] In many communication environments, the degree of fading effectsvaries dramatically both from time to time and from installation toinstallation. In the preferred embodiment, transmitters and receiverscommunicate using an optimal data segment size parameter by adapting thesize to conform to the communication environment of the network at anygiven time. For example, if a receiver detects repeated faultytransmissions, the data segment size parameter might be incrementallyreduced (under the assumption that fading caused the faults) until thedata throughput reaches an optimal level. Similarly, the size of thedata segment can be reduced based on a measured indication of the degreeof fading in the network.

[0118] One example of a receiver making such a measurement of fading canbe found in the abandoned patent application of Ronald L. Mahany, U.S.Ser. No. 07/485,313, filed Feb. 26, 1990, which is incorporated hereinby reference. Specifically, in that reference, a received signalstrength indicator (RSSI) circuit is found in the receiver. The RSSIcircuit samples the signal strength of a transmission. If the signalstrength samples are evaluated in sequence and the trend analyzed, thedegree of fading can be measured. If the signal strength samplesdecrease in value, it is likely that fading is present in the network.However, just because fading exists does not require segmentation. Onlyif fading causes the signal strength to drop below the level of thereceiver's sensitivity is segmentation required.

[0119] A fixed threshold value that is located a safe margain above thereceiver's sensitivity is used to determine whether to change the datasegment size. If a trend in signal strength shows values falling belowthe threshold, the data segment size is decreased. If the thresholdlevel is never reached, the segment size might be increased. Inaddition, the trend associated with a group of signal strength samplescan be used to predict the optimal data packet size—the intersection ofthe signal strength samples with the threshold defines a segment lengththat, with a safe margain, can be used effectively used with the currentdegree of fading.

[0120] After receiving a data segment, the receiver sends to thetransmitter indications regarding: 1) whether the data segment wasreceived without fault; and 2) what the new optimal segment size shouldbe. The transmitter responds by adjusting the data segment size and thensending the next segment. As can be appreciated, the data segments areadapted based on the previous transmission. Instead of adjusting on thebasis of the reception of a single data segment (the previoustransmission), other techniques for adjustment are contemplated. Forexample, the transmitter may also utilize a threshold window (orweighted averaging), inside of which the segment size will not bechanged. Only if the requested change by the receiver falls outside ofthe threshold window will the segment size change. Similarly, thereceiver might also utilize such a window—only requesting a change whenthe newly forecasted, optimal segment size falls outside of the window.

[0121] Direct-sequence Spread Spectrum Parameters.

[0122] As described above, the network controller provides an interfaceto both the older generation UHF radio transceivers and newer generationspread spectrum transceivers. A spread spectrum broadcasting system usesa sequential pseudo-noise signal to spread a signal that is in arelatively narrow band over a wider range of frequencies. It is thesubject of standards issued by the Federal Communications Commission(FCC) that provide usable spectrum at low power levels for communicationin limited areas such as warehouses, office buildings, and the like. Theuse of spread-spectrum techniques minimizes interference with othersusing the same channels in the spectrum.

[0123] A transmitter using direct-sequence spread spectrum transmissionuses a spreading-code of a higher frequency than that of the data rateto encode the data to be sent. This higher frequency is achieved byincreasing the chip clock rate (wherein each chip constitutes an elementof the spreading-code). Using the same spreading code, the receiverdecodes the received signal while ignoring minor faults which occurredin transmission, providing noise immunity and multipath signalrejection. The frequency and length of the spreading-code can be variedto offer more or less multipath signal rejection or noise immunity.Although it may result in improved communication, increasing thefrequency or length of the spreading-code requires additional overheadwhich may not be justifiable unless necessary.

[0124] Frequency-hopping Spread Spectrum Parameters.

[0125] Frequency-hopping is the switching of transmission frequenciesaccording to a sequence that is fixed or pseudo-random and that isavailable to both the transmitter and receiver. Adaptation to thecommunication environment via an exchange in frequency-hopping operatingparameters is possible, for example, via selective control of thehopping rate or through the use of coding or interleaving. The greaterthe degree of frequency selectivity of the fading envelope (i.e., whenfading is significant only over a portion of the spectrum of hoppingfrequencies), the greater the benefit of such adaptation.

[0126] Particularly, a parameter indicating the hopping rate can bevaried to minimize the probability that the channel characteristics willdetrimentally change during the course of a communication exchange. Tovary the hopping rate is to vary the length of a hopping frame. Althoughmultiple data (or message) exchanges per hopping frame is contemplated,the preferred hopping frame consists of a single exchange of data. Forexample, in a polling environment, the hopping frame might consistof: 1) a base station transmitting a polling packet to a roamingterminal; 2) the roaming terminal transmitting data in response; and 3)the base station responding in turn by transmitting an acknowledgepacket. Each hopping frame exchange occurs at a differentpseudo-randomly chosen frequency.

[0127] For optimization, the hop frame length is adjusted to be as longas possible, while remaining shorter than the coherence time of thechannel by some safety margin. Although such adjustment does noteliminate the effects of fading, it increases the probability that thecharacteristics of the channel will remain consistent during eachhopping frame. Thus, in the preferred embodiment, if the polling packettransmission is successfully received, the probability of successfulreceipt of the data (or message) and acknowledge is high.

[0128] Another parameter for changing frequency-hopping performance isthat of coding. Coding on the channel for error correction purposes canbe selectively used whenever the probability of data or message loss dueto fading is high. In particular, coding methods which provide bursterror correction, e.g., Reed-Solomon coding, can be applied if the hoplength is likely to exceed the coherence time of the channel. Suchcoding methods allow some portion of the data to be lost andreconstructed at the expense of a 30-50% reduction in throughput. Theoperating parameter for coding indicates whether coding should be usedand, if so, the type of coding to be used.

[0129] An operating parameter indicating whether interleaving should beused also helps to optimize the communication channel. Interleavinginvolves breaking down the data into segments which are redundantlytransmitted in different hopping frames. For example, in a three segmentexchange, the first and second segments are sequentially combined andsent during a first hopping frame. In a subsequent hopping frame, thesecond and third segments are combined and sent. Finally, the third andfirst segments are sequentially combined and transmitted in a thirdhopping frame. The receiving transceiver compares each segment receivedwith the redundantly received segment to verify that the transmissionwas successful. If errors are detected, further transmissions must bemade until verification is achieved. Once achieved, the transceiverreconstructs the data from the segments.

[0130] Other methods of interleaving are also contemplated. For example,a simpler form of interleaving would be to sequentially send the datatwice without segmentation on two different frequencies (i.e., on twosuccessive hops).

[0131] As can be appreciated, interleaving provides for a redundancycheck but at the expense of data or message throughput. The interleavingparameter determines whether interleaving is to be used and, if so, thespecific method of interleaving.

[0132] In addition, any combination of the above frequency-hoppingparameters might interact to define an overall operating configuration,different from what might be expected from the sum of the individualoperating parameters. For example, selecting interleaving and coding,through their respective parameters, might result in a more complexcommunication scheme which combines segmentation and error correction insome alternate fashion.

[0133] Source Encoding Parameters (For Narrowband Applications).

[0134] In the United States, data communication equipment operating inthe ultra-high frequency (UHF) range under conditions of frequencymodulation (FM) is subject to the following limitations.

[0135] (1) The occupied band width is sixteen kilohertz maximum withfive kilohertz maximum frequency deviation.

[0136] (2) The channel spacing is 25 kilohertz. This requires the use ofhighly selected filtering in the receiver to reduce the potential forinterference from nearby radio equipment operating on adjacent channels.

[0137] (3) The maximum output power is generally in the range of ten tothree hundred watts. For localized operation in a fixed location,however, transmitter power output may be limited to two watts maximum,and limitations may be placed on antenna height as well. Theserestrictions are intended to limit system range so as to allow efficientre-use of frequencies.

[0138] For non-return to zero (NRZ) data modulation, the highestmodulating frequency is equal to one half the data rate in baud. Maximumdeviation of five kilohertz may be utilized for a highest modulationfrequency which is less than three kilohertz, but lower deviations aregenerally required for higher modulation frequencies. Thus, at a datarate of ten thousand baud, and an occupied bandwidth of sixteenkilohertz, the peak FM deviation which can be utilized for NRZ data maybe three kilohertz or less.

[0139] Considerations of cost versus performance tradeoffs are the majorreason for the selection of the frequency modulation approach used inthe system. The approach utilizes shaped non-return-to-zero (NRZ) datafor bandwidth efficiency and non-coherent demodulation using alimiter-discriminator detector for reasonable performance at weak RFsignal levels. However, the channel bandwidth constraints limit themaximum data “high” data rate that can be utilized for transmitting NRZcoded data. Significant improvements in system throughput potential canbe realized within the allotted bandwidth by extending the concept ofadaptively selecting data rate to include switching between sourceencoding methods. The preferred approach is to continue to use NRZcoding for the lower system data rate and substitute partial response(PR) encoding for the higher rate. The throughput improvements of aNRZ/PR scheme over an NRZ/NRZ implementation are obtained at the expenseof additional complexity in the baseband processing circuitry. Anexample of a transceiver using such an approach can be found in thepreviously incorporated patent application of Ronald L. Mahany, U.S.Ser. No. 07/485,313, filed Feb. 26, 1990.

[0140] Partial response encoding methods are line coding techniqueswhich allow a potential doubling of the data rate over NRZ encodingusing the same baseband bandwidth. Examples of PR encoding methodsinclude duobinary and modified duobinary encoding. Bandwidth efficiencyis improved by converting binary data into three level, orpseudo-ternary signals. Because the receiver decision circuitry mustdistinguish between three instead of two levels, there is a signal tonoise (range) penalty for using PR encoding. In an adaptive baud rateswitching system, the effects of this degradation are eliminated byappropriate selection of the baud rate switching threshold.

[0141] Since PR encoding offers a doubling of the data rate of NRZencoded data in the same bandwidth, one possible implementation of aNRZ/PR baud rate switching system would be a 4800/9600 bit/sec system inwhich the low-pass filter bandwidth is not switched. This might bedesirable for example if complex low-pass filters constructed ofdiscrete components had to be used. Use of a single filter could reducecircuit costs and printed circuit board area requirements. This approachmight also be desirable if the channel bandwidth were reduced below whatis currently available.

[0142] The preferred implementation with the bandwidth available is touse PR encoding to increase the high data rate well beyond the 9600bit/sec implementation previously described. An approach using 4800bit/sec NRZ encoded data for the low rate thereby providing highreliability and backward compatibility with existing products, and 16Kbit/sec PR encoded transmission for the high rate may be utilized. ThePR encoding technique is a hybrid form similar to duobinary and severalof its variants which has been devised to aid decoding, minimize theincrease in hardware complexity, and provide similar performancecharacteristics to that of the previously described 4800/9600 bit/secimplementation. While PR encoding could potentially provide a high datarate of up to 20K bit/sec in the available channel bandwidth, 16Kbit/sec is preferable because of the practical constraints imposed byoscillator temperature stability and the distortion characteristics ofIF bandpass filters.

[0143] Exchanging Parameters.

[0144] All of the above referenced parameters must be maintained inlocal memory at both the transmitter and the receiver so that successfulcommunication can occur. To change the communication environment bychanging an operating parameter requires both synchronization betweenthe transceivers and a method for recovering in case synchronizationfails.

[0145] In a preferred embodiment, if a transceiver receiving atransmission (hereinafter referred to as the “destination”) determinesthat an operating parameter needs to be changed, it must transmit arequest for change to the transceiver sending the transmission(hereinafter the “source”). If received, the source may send an firstacknowledge to the destination based on the current operating parameter.Thereafter, the source modifies its currently stored operatingparameter, stores the modification, and awaits a transmission from thedestination based on the newly stored operating parameter. The sourcemay also send a “no acknowledge” message, rejecting the requestedmodification.

[0146] If the first acknowledge message is received, the destinationmodifies its currently stored operating parameter, stores themodification, sends a verification message based on the newly storedoperating parameter, and awaits a second acknowledge message from thesource. If the destination does not receive the first acknowledge, thedestination sends the request again. If after several attempts the firstacknowledge is not received, the destination modifies the currentlystored parameter, stores the modification as the new operatingparameter, and, based on the new parameter, transmits a request foracknowledge. If the source has already made the operating parametermodification (i.e., the destination did not properly receive the firstacknowledge message), the destination receives the request based on thenew parameters and responds with a second acknowledge. After the secondacknowledge is received, communication between the source anddestination based on the newly stored operating parameter begins.

[0147] If the destination does not receive either the first or thesecond acknowledge messages from the source after repeated requests, thedestination replaces the current operating parameter with a factorypreset system-default (which is also loaded upon power-up). Thereafter,using the system-default, the destination transmits repeated requestsfor acknowledge until receiving a response from the source. Thesystem-default parameters preferably define the most robustconfiguration for communication.

[0148] If after a time-out period the second request for acknowledgebased on the newly stored operating parameters is not received, thesource restores the previously modified operating parameters and listensfor; a request for acknowledge. If after a further time-out period arequest for acknowledge is not received, the source replaces the currentoperating parameter with the factory preset system-default (which is thesame as that stored in the destination, and which is also loaded uponpower-up). Thereafter, using the common system-default, the sourcelistens for an acknowledge request from the destination. Once received,communication is re-established.

[0149] Other synchronization and recovery methods are also contemplated.For example, instead of acknowledge requests originating solely from thedestination, the source might also participate in such requests.Similarly, although polling is the preferred protocol for carrying outthe communication exchanges described above, carrier-sensemultiple-access (CSMA) or busy tone protocols might also be used.

[0150] In addition, Appendix F provides a list of the program moduleswhich are found in Appendix G. These modules comprise another exemplarycomputer program listing of the source code (“C” programming language)used by the network controllers and intelligent base transceivers of thepresent invention. Note that the term “AMX” found in Appendices F and Grefers to the operating system software used. “AMX” is a multitaskingoperating system from KADAK Products, Ltd., Vancouver, B.C., Canada.

[0151] As is evident from the description that is provided above, theimplementation of the present invention can vary greatly depending uponthe desired goal of the user. However, the scope of the presentinvention is intended to cover all variations and substitutions whichare and which may become apparent from the illustrative embodiment ofthe present invention that is provided above, and the scope of theinvention should be extended to the claimed invention and itsequivalents. It is to be understood that many variations andmodifications may be effected without departing from the scope of thepresent disclosure.

What is claimed is:
 1. A data communication system for collecting andcommunicating data using RF data signal transmission, comprising: afirst terminal having transmission and reception capability from whichcommunication is desired; a second terminal having transmission andreception capability to which communication from said first terminal isdesired; said first and second terminals being responsive to anoperating parameter for determining and maintaining the operation oftransmission and reception; means within said second terminal that isresponsive to transmissions received from said first terminal forevaluating the current data communication system; means responsive tosaid evaluation means for determining whether a change in the operatingparameter should be made; and means within said first terminal that isresponsive to said determination means for changing the operatingparameter.
 2. The data communication system of claim 1 wherein saiddetermination means bases its inquiry on the percentage of RF signalswhich have been successfully received.
 3. The data communication systemof claim 1 wherein said evaluation means bases its evaluation on thesignal strength of the received RF signal.
 4. The data communicationsystem of claim 1 wherein said evaluation means comprises a measuringcircuit that produces a signal indicative of the signal strength ofreceived RF signals, and said determination means basing itsdetermination on the signal produced by said measuring circuit.
 5. Thedata communication system of claim 4 wherein said evaluation meansutilizes a threshold for making its evaluation.
 6. The datacommunication system of claim 4 wherein said determination meansutilizes a threshold window for making its determination.
 7. The datacommunication system of claim 1 wherein said operating parameterindicates the size of data segments to be transmitted.
 8. The datacommunication system of claim 7 wherein said determination means basesits determination on the percentage of RF signals that have beensuccessfully received.
 9. The data communication system of claim 7wherein said evaluation means comprises a measuring circuit thatproduces a signal indicative of the signal strength of received RFsignals, and said determination means bases its determination on thesignal produced by said measuring circuit.
 10. The data communicationsystem of claim 1 having spread spectrum communication capabilitywherein said operating parameter indicates the length of the spreadingcode for spread spectrum communication.
 11. The data communicationsystem of claim 10 wherein said evaluation means bases its evaluation onthe percentage of RF signals that have been successfully received. 12.The data communication system of claim 10 wherein said evaluation meanscomprises a measuring circuit that produces a signal indicative of thesignal strength of received RF signals, and said determination meansbases its determination on the signal produced by said measuringcircuit.
 13. The data communication system of claim 1 having spreadspectrum communication capability wherein said operating parameterindicates the chip clock rate of the spreading code for direct-sequencespread spectrum communication.
 14. The data communication system ofclaim 14 wherein said determination means bases its determination on thepercentage of RF signals that have been successfully received.
 15. Thedata communication system of claim 14 wherein said evaluation meanscomprises a measuring circuit that produces a signal indicative of thesignal strength of received RF signals, and said determination meansbases its determination on the signal produced by said measuringcircuit.
 16. The data communication system of claim 1 havingfrequency-hopping spread spectrum communication capability wherein saidoperating parameter defines characteristics of frequency-hoppingtransmissions.
 17. The data communication system of claim 16 whereinsaid evaluation means bases its evaluation on the percentage of RFsignals that have been successfully received.
 18. The data communicationsystem of claim 16 wherein said evaluation means comprises a measuringcircuit that produces a signal indicative of the signal strength ofreceived RF signals, and said determination means bases itsdetermination on the signal produced by said measuring circuit.
 19. Thedata communication system of claim 1 having frequency-hopping spreadspectrum communication capability wherein said operating parameterindicates the hopping rate.
 20. The data communication system of claim19 wherein said evaluation means bases its evaluation on the percentageof RF signals that have been successfully received.
 21. The datacommunication system of claim 19 wherein said evaluation means comprisesa measuring circuit that produces a signal indicative of the signalstrength of received RF signals, and said determination means bases itsdetermination on the signal produced by said measuring circuit.
 22. Thedata communication system of claim 1 having frequency-hopping spreadspectrum communication capability wherein said operating parameterindicates whether coding is to be used, and, if so, the type of coding.23. The data communication system of claim 22 wherein said evaluationmeans bases its evaluation on the percentage of RF signals that havebeen successfully received.
 24. The data communication system of claim22 wherein said evaluation means comprises a measuring circuit thatproduces a signal indicative of the signal strength of received RFsignals, and said determination means bases its determination on thesignal produced by said measuring circuit.
 25. The data communicationsystem of claim 1 having frequency-hopping spread spectrum communicationcapability wherein said operating parameter indicates whetherinterleaving is to be used, and, if so, the type of interleaving. 26.The data communication system of claim 22 wherein said evaluation meansbases its evaluation on the percentage of RF signals that have beensuccessfully received.
 27. The data communication system of claim 22wherein said evaluation means comprises a measuring circuit thatproduces a signal indicative of the signal strength of received RFsignals, and said determination means bases its determination on thesignal produced by said measuring circuit.
 28. The data communicationsystem of claim 1 having RF source encoding wherein said operatingparameter indicates the type of source encoding to be used inmaintaining RF communication.
 29. The data communication system of claim28 wherein said evaluation means bases its evaluation on the percentageof RF signals that have been successfully received.
 30. The datacommunication system of claim 28 wherein said evaluation means comprisesa measuring circuit that produces a signal indicative of the signalstrength of received RF signals, and said determination means bases itsdetermination on the signal produced by said measuring circuit.
 31. Adata communication system for collecting and communicating data in theform of RF signals comprising: a plurality of RF transceivers that storeand modify a variable operating parameter; each of said transceiverscontrolling the operation of transmission and reception based on thestored of parameter; means within said transceivers for evaluating thestored parameter based on each transmission received; means responsiveto said evaluation means for determining whether the operating parametershould be modified; and said plurality of RF transceivers responding tosaid determination means by storing modified operating parameters. 32.The data communication system of claim 31 wherein said operatingparameter indicates the size of data segments to be transmitted.
 33. Thedata communication system of claim 31 having spread spectrumcommunication capability wherein said operating parameter indicates thelength of the spreading code for spread spectrum communication.
 34. Thedata communication system of claim 31 having spread spectrumcommunication capability wherein said operating parameter indicates thechip clock rate of the spreading code for direct-sequence spreadspectrum communication.
 35. The data communication system of claim 31having frequency-hopping spread spectrum communication capabilitywherein said operating parameter defines characteristics offrequency-hopping transmissions.
 36. The data communication system ofclaim 31 having frequency-hopping spread spectrum communicationcapability wherein said operating parameter indicates the hopping rate.37. The data communication system of claim 31 having frequency-hoppingspread spectrum communication capability wherein said operatingparameter indicates whether coding is to be used, and, if so, the typeof coding.
 38. The data communication system of claim 31 havingfrequency-hopping spread spectrum communication capability wherein saidoperating parameter indicates whether interleaving is to be used, and,if so, the type of interleaving.
 39. The data communication system ofclaim 31 having RF source encoding wherein said operating parameterindicates the type of source encoding to be used in maintaining RFcommunication.
 40. The data communication system of claim 31 furthercomprising: means within said transceivers being responsive to a seriesof failed communication exchanges for replacing said stored operatingparameter with a system default value.
 41. A data communication systemfor collecting and communicating data using RF data signal transmission,comprising: a first terminal having transmission and receptioncapability from which communication is desired; a second terminal havingtransmission and reception capability to which communication from saidfirst terminal is desired; said first and second terminals beingresponsive to an operating parameter for determining and maintaining theoperation of transmission and reception; means within said secondterminal being responsive to transmissions received from said firstterminal for evaluating the performance of the transmission; meanswithin said second terminal for determining whether a change in theoperating parameter is needed, and, if so, for transmitting a requestfor change signal to said first terminal; said first terminal respondingto a received request for change signal by transmitting an acknowledgesignal then modifying and storing the operating parameter; and means atsaid second terminal responsive to the acknowledge signal for modifyingand storing the operating parameter.
 42. The data communication systemof claim 41 further comprising: means at said terminals being responsiveto a series of failed communication exchanges for replacing said storedoperating parameter with a system default value.
 43. The datacommunication system of claim 42 wherein said operating parameterindicates the size of data segments to be transmitted.
 44. The datacommunication system of claim 42 having spread spectrum communicationcapability wherein said operating parameter indicates the length of thespreading code for spread spectrum communication.
 45. The datacommunication system of claim 42 having spread spectrum communicationcapability wherein said operating parameter indicates the chip clockrate of the spreading code for direct-sequence spread spectrumcommunication.
 46. The data communication system of claim 42 having RFsource encoding wherein said operating parameter indicates the type ofsource encoding to be used in maintaining RF communication.
 47. The datacommunication system of claim 42 having frequency-hopping spreadspectrum communication capability wherein said operating parameterdefines characteristics of frequency-hopping transmissions.